Long-term exposure to air pollution can lead to physical changes in the brain, as well as learning and memory problems and even depression, new research in mice suggests.

While other studies have shown the damaging effects of polluted air on the heart and lungs, this is one of the first long-term studies to show the negative impact on the brain, said Laura Fonken, lead author of the study and a doctoral student in neuroscience at Ohio State University. The study appears online this week in the journal Molecular Psychiatry.

For this study, Fonken and colleagues in Ohio State’s Department of Neuroscience collaborated with researchers in the university’s Davis Heart and Lung Research Institute.

In previous studies in mice, the Davis research group—including Qinghua Sun, associate professor of environmental health sciences, and Sanjay Rajagopalan, professor of cardiovascular medicine—found that fine air particulate matter causes widespread inflammation in the body, and can be linked to high blood pressure, diabetes and obesity. This new study aimed to extend their research on air pollution to the brain.

The more we learn about the health effects of prolonged exposure to air pollution, the more reasons there are to be concerned. This study adds more evidence of pollution’s negative effects on health.

—Randy Nelson, co-author of the study and professor of neuroscience and psychology at Ohio State

In the new study, mice were exposed to either filtered air or polluted air for six hours a day, five days a week for 10 months&MDASH;nearly half the lifespan of the mice. The polluted air contained fine particulate matter (PM2.5, which can reach deep areas of the lungs and other organs of the body.

“This could have important and troubling implications for people who live and work in polluted urban areas around the world.”

—Laura Fonken

The concentration of particulate matter that the mice were exposed to was equivalent to what people may be exposed to in some polluted urban areas, according to the researchers.

After 10 months of exposure to the polluted or filtered air, the researchers performed a variety of behavioral tests on the animals.

In a learning and memory test, mice were placed in the middle of a brightly lit arena and given two minutes to find an escape hole leading to a dark box where they feel more comfortable. They were given five days of training to locate the escape hole, but the mice who breathed the polluted air took longer to learn where the escape hole was located. The mice exposed to polluted air also were less likely to remember where the escape hole was when tested later.

In another experiment, mice exposed to the polluted air showed more depressive-like behaviors than did the mice that breathed the filtered air. The polluted-air mice showed signs of higher levels of anxiety-like behaviors in one test, but not in another.

But how does air pollution lead to these changes in learning, memory and mood? The researchers did tests on the hippocampal area of the mice brains to find the answers. The hippocampus is associated with learning, memory and depression.

Results showed clear physical differences in the hippocampi of the mice who were exposed to polluted air compared to those who weren’t. The researchers looked specifically at dendrites (branches that grow off of nerve cells). The dendrites have small projections growing off them called spines, which transmit signals from one neuron to another.

Mice exposed to polluted air had fewer spines in parts of the hippocampus, shorter dendrites and overall reduced cell complexity.

“Previous research has shown that these types of changes are linked to decreased learning and memory abilities,” said Nelson.

In other studies, several of the co-authors of this study from the Davis research center found that chronic exposure to polluted air leads to widespread inflammation in the body, which is linked to a variety of health problems in humans, including depression. This new study found evidence that this low-grade inflammation is evident in the hippocampus.

In mice that breathed the polluted air, chemical messengers that cause inflammation—called pro-inflammatory cytokines—were more active in the hippocampus than they were in mice who breathed the filtered air.

The hippocampus is particularly sensitive to damage caused by inflammation. We suspect that the systemic inflammation caused by breathing polluted air is being communicated to the central nervous system.

—Laura Fonken

The research was supported by grants from the National Institutes of Health.

Of course, with 100M cars burning gasoline and oil driving around we are ALL exposed to toxic substances in the air. It is doubtful however, that depression in sunlit areas like the US southwest will ever exceed the per capita depression of Scandinavia, or Russia.

Exposure to light has a far greater effect on the human psyche than particulates.

"Deniers" don't question emissions, especially particulates, HarveyD. We question the b.s. link between CO2 and "warming." Of course, you Warmists love calling names and attempting to blanket our skepticism into all anti-environmentalism categories. Name calling is so much easier than fact finding.

#3 Selecting or cherry picking sources: picking the weakest papers or only ones that are contrary. Particularly worrisome is looking at only a single study, particularly in medicine, as one study rarely conclusively proves something. Note that this includes anecdotal evidence and quote mining.

#4 Demanding impossible standards for research (often with moving goalposts).

#5 Use of fallacy, including misrepresentation and false analogy. Informally, this can include a witch's brew of half-truths, sob stories, and/or spin to try to force the public to ignore an important issue.

Most (not all) spend, tax and spend liberals have common well known traits, basically:
1. Don’t drill because if we have to import oil, we won’t use oil.
2. Little or No concern for what anything costs, just what they want.
3. China has more effective anti-pollution laws than the US.
4. Government run health care will cost less & provide more – never mind all unions, big DNC donors & politicians can opt out.
5. Government should control everything.
8. Everything in hands of the government, private enterprises are uncontrolled evil.
9. etc etc

#1 The identification of perceived conspiracies (including belief of corrupted peer review and inversionism). OK BUT. They were identified, not just perceived. Maybe too much was made of those emails but the email denialists are more delusional than the AGW denialists.

#2 The use of fake experts (often with the smearing of real experts). OK

#5 Use of fallacy, misrepresentation and false analogy. OK, but see #1

#6. The Warmists must realize that, like socialists, they expect close to 100% of the world to act in unison against their own best interests. (Don’t pretend that unilateral GHG emission reduction is almost certainly self destructive)
When in reality, the “high points” of the AGW movement; UNFCCC in 1992, Kyoto, Copenhagen, COP16 at Cancun in 2010, show (even prove) that voluntary reduction of GHGs will never work.

Is anyone even claiming that any nation has reversed GHG emissions?
Totalitarianism would be required first.
But wait, those of you that like such government, GHG emission reduction would then be of lower priority; look at China.
No, no – I did not say listen. to what China says, I said look at China.

These lists are more amusing than Letterman's. Harvey... You are sounding more paranoid than ai_vin!!

5. drive USA back to the 15th century where they effectively become Kings and Lords and we become their unpaid servants.

Fifteenth century North America was inhabited solely by Native Americans numbering around 10M. There were no Kings & Lords and no servants even after Columbus and Vespucci claimed the continent for their authorities.

Unregulated or poorly regulated free enterprise is a real Monopoly Game. Some 3M millionaires and 300 to 3000 Billionaires are still playing. By the end of the century, as few as 30 trillionaires may be playing. Eventually one or two multi-trillionaire will run the game.

Unfortunately, the majority does not see it coming and still believe that they will be included into this Monopoly game.

Drastically raising the CO2 level and other GHG in the atmosphere and subsequent AGW is simply cause and effect. When the earth absorbs the radiant energy from the sun yet the earth can't radiate back to space as much due to the blanketing effect of the GHG's mean that the earth's temp must rise a bit until the energy balance is established. This is pure science and quite easy to understand. A little rise in earth temp will cause more H2O vapor in the atmosphere and will retain even more heat unless earth's temp will rise even more.

We simply have to reverse what we had done to the planet in order to avert catastrophe.